The actions of many hormones are thought to be generated by stimulation of adenylate cyclase. In recent years rapid advancement has been made in characterizing the interaction of hormone with receptor, but much remains to be learned about the molecular interaction of receptor or hormone-receptor with adenylate cyclase. The major purpose of this project is to understand at a molecular level, the interactions and regulation of the hormone-receptor-adenylate cyclase complex in native membranes. The aims of the proposal are to purify cardiac adenylate cyclase and study its interplay with hormone receptor, particularly the beta-adrenergic receptor. It is specifically proposed over the next three years to: 1. purify and characterize cardiac beta-adrenergic receptor; 2. prepare a homogenous specific antibody against the beta-adrenergic receptor; 3. purify canine cardiac adenylate cyclase to homogeneity; 4. characterize the adenylate cyclase preparation; 5. characterize the specificity of reassociation of adenylate cyclase with native membranes and examine its interaction with various endogenous membrane hormone receptors; 6. examine the kinetics and specificity of hormonal response with the supplanted adenylate cyclase; and 7. determine the interaction of receptor with adenylate cyclase in the desensitized state and the regulation and renewal of the desensitization process.